Starting in January, shortly after becoming the Senate Democrats’ political outreach chair, Sanders helped organize health-care rallies meant to preempt any repeal of the ACA. Throughout 2017, Sanders used campaign funds (he is running for reelection in 2018) to give speaking tours in the states of senators who were seen as on the fence about repeal....

The news of next week’s CNN debate jogged their memories of a similar CNN event in February, where Sanders and Sen. Ted Cruz (R-Tex.) sparred over health care. At the time, Sanders pivoted from Cruz’s attacks on the ACA to his own arguments for universal care, including praise of single-payer systems in Europe.

“That was a very different moment in this debate,” said Miller-Lewis. “Bernie’s been saying for months that he knows single-payer isn’t going to pass next week. This is about making the argument to save the ACA.”

If you're a repeal opponent, the Sanders rhetoric in his rallies earlier this year was partly reassuring, partly unsettling. Here's what he said in Macomb County, Michigan, shortly before Trump's inaugural:

"Let me be very clear, there are differences of opinion on the Affordable Care Act — some people like it, some people don't like it — but very few Americans believe that we should repeal the Affordable Care Act without a replacement program to make it better. We are saying to our Republican colleagues: We will not let you throw up to 30 million Americans off of health insurance."

If Sanders emphasizes the latter point -- that it's unconscionable to vote for a replacement that will make healthcare worse -- then he'll be all right. If not....

Obamacare is on the line, but so is Sanders's status as a national leader. The conventional wisdom is that Democrats are hopelessly split between a Sanders wing and a Hillary Clinton wing -- but as a HuffPost/YouGov poll recently noted, 71% of Democrats and Democratic-leaning independents view Clinton favorably and 73% view Sanders favorably. Most Democrats like both of them.

But what if Sanders's critics are right? What if he's less than enthusiastic about Obamacare, and is perceived as losing the debate for the pro-Obamacare side? And what if Republicans then succeed in passing Graham-Cassidy?

He could come to be seen as the man who killed Obamacare. Some people who think that that creates a huge opening for single payer will be happy -- but single payer can't be debated seriously until 2021 at the earliest, and in the meantime we'll be living in the Trumpcare era. A lot of people are not going to be happy. A lot of people are going to start losing coverage. The suffering is going to begin. Many people who now think of Sanders as a leader of Democrats (even though he's not a member of the party) are going to hold him accountable for that.

Sanders critics tend to be more optimistic about the other member of the anti-Trumpcare debate team, Minnesota senator Amy Klobuchar. I just hope she's a powerful enough defender of Obamacare. Here she is in a July TV appearance in Minnesota:

"I said the day the Affordable Care Act passed, this is a beginning and not an end, and we need to make changes," she says. I hope she doesn't undermine the law from the left-center as Sanders undermines it from the social democratic left. You can be sure that Graham and Cassidy won't be conceding many points.